The present invention relates to a valve that automatically regulates operating partial vacuum in milking systems, preferably with a main valve that admits atmospheric air into the partly vacuumized system and that has a control chamber subject to calibrated admission of air from the atmosphere and communicating with the control chamber of an auxiliary valve through a choke point that can be blocked by the auxiliary valve, whereby the auxiliary-valve control chamber communicates with a series of lines that supplies the operating partial vacuum.
A valve of this type is known, for example, from German Patent No. 2 363 125. With it, the desired operating partial vacuum can be established by varying the prestress of a spring. Since the operating partial vacuum in milking systems must conform to standards that have been established for the dairy industry, it must be adjusted by an expert when the system goes into initial operation. The level of operating partial vacuum must not be altered by the operator of the milking system to prevent possible detriment to the operation of the system and to the health of the animals. Once the level has been set it must accordingly not even be varied while the milking system is being rinsed out. The effectiveness of the rinsing process depends, however, on the speed at which the rinsing solution travels through the system and hence on the level of partial vacuum. It would therefore be desirable to use a higher vacuum during the rinsing process.
Operations have accordingly been conducted to some extent with two regulating valves, one set at the partial vacuum employed during the milking process and the other at the more powerful partial vacuum employed to rinse the system out. Switching from one valve to the other can be either manual or automatic. The expense of installing the system is, however, considerably increased by the second valve.